An automatic transmission has a plurality of selectively engageable clutches engageable in different combinations to establish multiple different gears having different ratios of torque of an output member to torque of an input member. A controller can command that the transmission shift between the different gears in response to driver input, or in response to vehicle operating conditions such as vehicle speed, input or output torque, and other conditions.
Some transmissions may be configured so that a shift between two gears is a double transition shift. A double transition shift requires that two of the clutches that are engaged in the current gear be disengaged in the commanded gear, and two other clutches not engaged in the current gear be engaged in the commanded gear. These are referred to as transitioning clutches. Double transition shifts generally require slipping at least some of the transitioning clutches during the shift. However, if one of the clutches involved in the shift has a slip direction in the current gear and an opposite torque direction (i.e., direction in which the clutch carries torque) in the commanded gear, or a torque direction in the current gear and an opposite slip direction in the commanded gear, then that clutch cannot provide reaction torque during the shift and still allow a desired output torque and input acceleration during the shift.